Many industrial processes are effected to provide heat and mass transfer to a material. Increased rates of heat and mass transfer are desired to increase the efficiency and productivity of such processes. Applications for such processes include food processing, carpet and textiles manufacturing, packaging and sealing, wood fiber processing, glass forming, sheet metal forming, and drying, curing, baking, sintering and like heat treating processes for a wide range of materials and compositions.
Many such industrial processes are implemented by the use of a conveyor that moves the material through a space where it may be impinged or otherwise acted upon by a combustion system to accomplish the desired heat and mass transfer. One known arrangement provides an enclosure heated by a combustion system and having entrance and exit apertures for conveying material therethrough to direct and apply heat to the material, as illustrated by the drying and curing oven of U.S. Pat. No. 4,061,463 to Bennett.
Additionally, there are known combustion systems that provide a pulsating combustion cycle. The general operational principle of such pulse combustion systems is that a fuel/air mixture is ignited within a combustion chamber which increases the pressure therein resulting in exhaustion of the combustion products from the combustion chamber causing a subsequent pressure decrease which draws additional fuel and air into the combustion chamber for ignition, thereby setting up a cycle of pulsing detonations.
Such pulse combustion systems generally provide several advantages over most non-pulsating systems, including the advantages of self-aspiration and higher thermal efficiency of the process. These systems may be self-aspirating because the above described pressure fluctuations cyclically draw combustion material into the combustion chamber to sustain the combustion process. Therefore, a blower is not required for supplying air after start-up. Additionally, these systems may provide a higher thermal efficiency because the pulsating cycles create acoustic pulse waves that break down boundary layers and thus provide for greater heat and mass transfer rates. Also, thermal efficiency may be increased by the pulsating cycles producing a greater mixing of fuel and air and thus providing for a more complete burning of the combustion materials.
One known type of pulse combustion system provides two burners connected in parallel to an air intake, with each burner operating at a phase difference of 180 degrees from the other burner, as illustrated by U.S. Pat. No. 2,838,102 to Reimers, U.S. Pat. No. 4,808,107 to Yokoyama et al., and U.S. Pat. No. 4,840,558 to Saito et al. These systems commonly include a heat exchanger for. heat transfer to a fluid for use in applications such as water and oil heating. There are no known anti-phase type self-aspirating or forced air pulse combustion systems adapted for directing and applying thermal and/or acoustic energy to a material in a conveyor type application.
Another known type of pulse combustion system provides a spherical combustion chamber with an air intake tube extending radially into the combustion chamber to provide a more central point of combustion within the chamber, and a resonant exhaust tube extending from the chamber, as illustrated by U.S. Pat. No. 2,719,710 to Haag et al. and U.S. Pat. No. 4,260,361 to Huber. Such centralized point of combustion generally does not promote complete combustion within the combustion chamber prior to exhaust because such systems generally do not produce the desired turbulence achieved by a fully developed thermal and acoustic pulse wave.
Additionally, there is known the combustion system of Saito et al., as described above, and the gas furnace system disclosed in U.S. Pat. No. 3,540,710 to Urawa, that each provide a combustion chamber with tangential air intake orifices. Neither of these combustion systems, however, have a resonant exhaust pipe system that efficiently propagates an acoustic and/or thermal pulse wave for application to a material, provide a point of combustion within the combustion chamber that sets up and fully develops the desired turbulence of an acoustic and/or thermal pulse wave, nor provide a combustion chamber that advantageously directs an acoustic and/or thermal pulse wave toward such an exhaust pipe system.
An additional deficiency of many known pulse combustion systems is the complicated valve and/or control systems employed to control combustion and heat output by regulating the flow rate and ratio of air and fuel, as illustrated by U.S. Pat. No. 4,808,107 to Yokoyama et al. discussed heretofore. Such complicated valve systems are often difficult to maintain in proper adjustment and operating order. A further deficiency of many pulse combustion systems is that generally the systems are necessarily designed for a specific application such as water heating, because the combustion chamber and exhaust pipe must be specifically designed to set up the desired natural harmonic frequency at which the system should operate.
Accordingly, what is needed but not found in the prior art is a combustion system and method that embodies pulse combustion principles in an apparatus for conveyor type heat and mass transfer processes for achieving increased thermal efficiency and self-aspiration, that provides a combustion chamber for setting up and fully developing high turbulence, high velocity thermal and acoustic pulse waves, that provides a resonant exhaust piping system for propagating and directing without impeding the thermal and acoustic pulse waves to a material, that provides for temperature control without the need for a complicated valving and control system, and that has a design that is modular, simple, and cost-effective to manufacture and use for a variety of different applications.